New thermometry method reveals cooling effect in compressed quantum gases

An international collaboration between researchers from Innsbruck and Geneva has unveiled a groundbreaking thermometry method tailored for measuring temperatures in low-dimensional quantum gases. Surprisingly, their findings suggest that compressing a gas may lead to cooling—a counterintuitive phenomenon that challenges conventional wisdom. Published in Science Advances, this study marks a significant milestone in our understanding of quantum systems in reduced dimensions.

In classical thermodynamics, the act of compression typically results in heating, while expansion leads to cooling—a principle familiar to anyone who has pumped up a bicycle tire. However, the rules governing the quantum realm introduce a new dimension of complexity. Here, particles exhibit unique behaviors: bosons can condense into a superfluid state, while fermions adhere to the Pauli exclusion principle, avoiding one another’s presence.

Reduced dimensions amplify the influence of quantum fluctuations, causing bosons to fermionize under strong inter-particle interactions. Consequently, quantum systems in one-dimensional (1D) configurations have emerged as a fertile ground for exploration, particularly in the context of quantum simulation and electronic circuitry miniaturization.

Employing an experimental platform involving cold atoms confined to tight light potentials, researchers from Innsbruck and Geneva conducted both experimental and theoretical investigations. Their groundbreaking discovery reveals that strongly interacting quantum many-body systems exhibit cooling when subjected to dimensional reduction—a phenomenon hitherto unforeseen in scientific literature.

This unexpected cooling effect arises from the interplay between strong lateral confinement in 1D and intense interactions, leading to boson fermionization. By developing a cutting-edge thermometry method boasting nano-Kelvin sensitivity, the research team achieved unparalleled precision in temperature measurement.

Lead author Yanliang Guo remarks, “We are able to measure temperatures in 1D with one nano-Kelvin sensitivity.” Their observations demonstrate that temperatures initially rise upon compression from three dimensions to two, only to decrease upon further compression to 1D.

Hanns-Christoph Nägerl, one of the team leaders, highlights the significance of these findings, emphasizing that even seemingly modest temperature reductions—from 12.5 to 9 nano-Kelvin—hold immense scientific value. Subsequent improvements have pushed temperature measurements down to 2 nano-Kelvin, with sensitivity reaching 1 nano-Kelvin.

Anticipating widespread interest within the scientific community, the team underscores the potential of low-dimensional, strongly correlated quantum systems to elucidate fundamental physics phenomena. Notably, these findings may hold implications for unraveling enigmatic phenomena such as high-temperature superconductivity—a puzzle with profound implications for various fields.

Thierry Giamarchi, the team leader from Geneva, reflects on the conceptual intrigue of temperature reductions with increased confinement—a phenomenon defying common intuition. Indeed, this discovery underscores the profound intricacies of the quantum world and underscores the transformative potential of interdisciplinary research in unlocking its mysteries.

Source: University of Innsbruck

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